Gaseous electric discharge lamp



y 1947. H. HAYNES ETAL 2,424,457

' GASEOUS ELECTRIC msdms LAIP Filed Sept. 30, 1944 mmmmwma I N VEN TURF-HUWARD HAYNES LYNN j [CKIS JP.

' THE/R A TTURNEY Patented July 22, 1947 Howard Haynes, Wllloughby,andLynn S. Ickis,,

Jr., East Cleveland, Ohio, auignors to General Electric Company, acorporation of New York Application Sept. :0, 1944, serial No. asse 12Claims. 176-425) Our invention relates; to gaseous electric dischargedevices.

Certain types of gaseous electric discharge lamps, such as hot orthermionic cathode fluorescent lamps now in extensive use and employingactivated filamentary electrodes at the ends of an elongated tubularenvelope, are started by passingcurrent through the electrodes topreheat them before application of a potential.

higher than the operating potential of the lamp to initiate thedischarge between the electrodes. This type oflamp is incapable ofstarting at the voltages applied thereto in the event the electrodeshave become deactivated. Repeated flashing of the lamp in unsuccessfulattempts to start is obviated by employing a suitable cut-out switchwhich opens the circuit therethrough, so that the lamp merely remainsunlighted to indicate the need for replacement.

However, certain other types of lamps employing activated thermionicelectrodes are started "cold," that is, the electrodes are not preheatedas described above. This type of starting necessitates the use of highervoltages, and the lamps do not extinguish themselves at the end of lifeas determined by electrode deactivation, particularly on high voltagecircuits (such as those commonly used in installations of the "neon signtube type), but continue to operate with abnormal heating of all metalparts of the electrode. trode may result in violent failure (such asshattering of the envelope) or damage to the socket.

Oneof the objects of our invention is to prevent such continuedoverheating of the electrode by extinguishing the discharge. Accordingto our invention this is accomplished by utilizing the abnormal heat toeffect introduction into the envelope of an atmosphere which is capableof quenching the discharge, or to put it another way, an atmospherewhich is incapable of supporting a discharge between the electrodes.Further objects and advantages of our invention will appear from thefollowing detailed description of species thereof and from the drawing.

In the drawing, Fig. 1 is a sectional view of one end of a gaseouselectric discharge lamp embodying our invention; Fig. 2 is a partialsection of a, modification, the left hand end of the lamp being shown asrotated about its longitudinal axis somewhat as compared to its righthand end; and Fig. 3 is a sectional view of one end of a furthermodification.

Referring to Fig. 1, the lamp shown therein is of the positive columntype comprising an elon The continued overheating of the elecgatedtubular glass envelope i which may be coated interiorly with a suitablefluorescent material and which contains a suitable gaseous atmosphere,such for example, as a few millimeters of argon and a small quantity ofmercury. A terminal contact member in the form of a disc or cap 2 ofsheet metal, such asa chrome-iron alloy known as "Allegheny 55, issealed by fusion directly to each end of the envelope. The form of discillustrated is like that disclosed in Patent 2,146,579, G. E. Inman,wherein the disc is inwardly embossed at 3, and is provided with anaperture 4 through which the envelope is exhausted and then filled withits gaseous atmosphere through a glass exhaust tube, the said aperturebeing subsequently sealed by the residue 5 of the exhaust tube.

At each end of the envelope is an activated filamentary electrode 6consisting, preferably, of a coiled tungsten wire activated by a coatingof alkaline earth oxides. The electrode 6 is supported from andelectrically connected to the disc 2 by a comparatively rigid wire I oneend of which is coiled around the embossment 3, as shown at 8. Ifdesired the end 8 of the wire i may be welded to the disc 2. The other,or free, end 9 of the wire I is shaped in the form of a U whichpreferably lies in a plane including the iongitudinal axis of theenvelope l. The extremity of the wire 1 is formed into a hook ill inwhich one end of the electrode 6 is clamped, while an intermediateportion thereof is doubled back upon itself in an S-shape to form a hookin which the other end of the electrode is clamped.

The U-shaped portion 9 of wire 1, togetherwith the electrode 6, therebyform a closed loop, so

that when the end of the lamp is inserted in the coil of a highfrequency oscillator, the loop permits the induction of currentssuflicient to heat the electrode 6 and activate it by converting theoriginal coating of alkaline earth carbonates to the correspondingoxides, preferably during evacuation of the envelope. The loop islocated in the lamp in a, plane perpendicular to the high frequencyfield. When necessary, a small wire 12 is threaded through the electrodecoil to reduce the resistance of that part of the loop to a value onlyslightly higher than that of the remainder of the loop.

The. lamp is operated by connecting it across any suitable source ofelectric energy which, for long lamps, may be a. high voltagetransformer such as those commonly used in "neon" sign typeinstallations. The discharge strikes through the gaseous filling betweenthe electrodes 8 at the 3 ends of the envelope. The electrodes arerapidly heated by the discharge to an electron-emitting temperature. Aslong as the electrodes remain properly activated, the ends of the lampare not unduly heated. However, when an electrode 6 becomes deactivatedby loss of activating oxides, although the current remains substantiallythe same, the voltage drop in the discharge increases with a resultingincreased wattage, and the support wire I becomes highly heated, withthe resuit that the envelope I may crack and be shattered, or sufficientheat maybe conducted through the disc 2 to fuse it to the socket inwhich the lamp is mounted, or otherwise damage the socket.

According to this invention, such action is eliminated by introducinginto the lamp a gas capable of extinguishing the discharge therein. Inthe form shown in Fig. 1, we provide within the envelope, a sealedampule or capsule l3 which is attached to the support wire I by a wireH.

The ampule I3 is made ofa material, or of such form (a locally weakenedportion, for example), that it is ruptured upon continued overheating.

of the electrode and its supporting structure, thereby evolving a gascapable of extinguishing the discharge in the lamp. To this end, theampule may be made of a glass which softens at the abnormally hightemperature then existing in the lamp. Y

The ampule I3 may be filled with an inorganic material which decomposesat the temperature of the electrode and its supporting structure afterdeactivation of the electrode. The ampule is then submitted to highpressure, and by selecting a glass for the ampule which softens at thosehigh temperatures, the ampule will open and introduce the products ofdecomposition into the arc stream to extinguish the discharge.

As an inorganic filling material for the ampule I3, we prefer at presentto use the ammonium sulphate (NH4)2SO4. However, we have successfullyused ammonium acetate, NH4C2I-BO2; ammonium phosphate, (NHozHPOl; andsodium bisulphate, NaHSOr. These substances are effective even in lampsoperating on high voltage circuits. It will be noted that thesesubstances are characterized by the fact that they break down to formwater vapor as one of the products of decomposition. However, in lampsoperated on low voltage circuits, successful results may be obtainedwith gaseous fillings such as hydrogen, air, CO2, C1, and S02.

The left hand end (not shown) of the lamp shown in Fig. 1 may be of thesame construction corresponding disc 2 need not be provided with anexhaust aperture 4 and tubulation 5.

In the form shown in Fig. 2, the right hand end of the lamp is providedwith an internal tubular glass appendage l5 which is sealed at its innerend but has its outer end in communication with. the atmosphere.Although the appendage may be attached to the envelope l, we prefer tofuse its outer end to the disc 2 around the aperture 4. An intermediateportion'of the wire I is coiled around the appendage IS. The left handend of the lamp contains a similar appendage l5 which is fusedaround asupplementary aperture 4' in disc 2 since that end of the lamp isevacuated through aperture 4, although, of course, the appendage couldbe attached around aperture 4 and the exhaust tube around aperture 4f.

In thev Fig. 2 lamp, deactivation of anelectrode 6 with resultantoverheating, causes an appendage I! to be punctured, usually at a pointunder a portion of the wire I in contact therewith, thereby admittingthe ambient atmosphere into the envelope with the result that thedischarge is extinguished.

In Fig. 3 the lead-in wire'l is provided with a bent V-shaped portion 16with its bight engaging the wall of the envelope I. In this case,overheating of the electrode 6 and wire 1 causes the envelope l to bepunctured at the point engaged by the portion iii of wire I, therebyadmitting air into the envelope to extinguish the discharge. A number oftests have demonstrated that a small puncture is produced in this waywithout shattering the envelope or cracking it around its circumference.

It will be' apparent to those skilled in the art that variousmodifications, omissions and substi- .as the right hand end with theexception that the tutions may be made within the scope of ourinvention.' We have successfully applied the invention, as illustratedin the several modifications disclosed herein, to elongated tubularfluorescent lamps of the low pressure mercury vapor type which operateat low temperatures.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. A gaseous electric discharge lamp comprising a sealed glass containercontainingspaced electrodes at least one of which is activated, saidcontainer being subject to uncontrolled fracture upon overheating at theactivated electrode due to deactivation thereof, and means sensitive tosuch overheating and effective to cause introduction into the container,rior to such uncontrolled fracture thereof, of a gaseous .materialhaving a quenching effect upon the discharge.

2. A gaseous electric discharge lamp comprising a sealed glass containercontaining spaced electrodes at least one of which is an activatedthermionic electrode carried by a lead-in conductor, said containerbeing subject to uncontrolled fracture upon overheating at the activatedelectrode due to deactivation thereof, and means including said lead-inconductor for effecting introduction into the container, uponoverheating of said conductor and prior'to such uncontrolled fracturethereof, of a gaseous material having a quenching effect upon thedischarge.

3. A gaseous electric discharge lamp comprising a sealed containercontaining spaced electrodes at least one of which is activated, and anampule adjacent the activated electrode and sealed from the atmospherewithin said container but rupturable upon overheating at said electrodedue to deactivation thereof to release a gaseous material having aquenching effect upon the discharge.

4. A gaseous electric discharge lamp comprising a sealed containercontaining spaced electrodes at least one of which is activated, and anampule adjacent the activated electrode and. sealed from the atmospherewithin said container but rupturable upon overheating at said electrodedue to deactivation thereof and containing an inorganic salt whichdecomposes to yield a gaseous material'having a quenching effect uponthe discharge.

5. A gaseous electric discharge lamp comprising a sealed containercontaining spaced electrodes at least one of which is activated, asupport wire for said electrode, an internal hollow appendage on saidcontainer sealed from the atmosphere within the container but open tothe external atmosphere, a portion of said support wire beinginengagement with said appendage and adapted to puncture said appendageupon overheating thereof due to deactivation of the electrode to admit.the surrounding atmosphere into the lamp and thus quench the dischargetherein.

6. A gaseous electric discharge lamp comprising a sealed glass envelopcontaining spaced electrodes at least one of which is activated, and asupport wire for said electrode having an intermediate portion thereofbent so that its bight engages the envelope wall and is adapted topuncture said wall upon overheating of said wire due to deactivation ofsaid electrode.

7. A gaseous electric discharge lamp comprising a sealed containercontaining spaced electrodes at least one of which is activated,supports for said electrodes, said container being subject touncontrolled fracture upon overheating at the activated electrode due todeactivation thereof, and means associated with the activated electrodesupport and operable upon overheating of the said electrode and itssupport due to'deactivation of an electrode for introducing into thedischarge electrode support to be ruptured byheat there-- from.

8. A gaseous electric discharge lamp comprising a sealed containercontaining spaced electrodes at least oneof which is activated, and 'asealed ampule adjacent the activated electrode and rupturable uponoverheating at said electrode due to deactivation thereof and containingan ammonium salt which is stable at the normal operating temperature ofthe lamp but upon such overheating decomposes to yield a gaseousmaterial having a quenching effect upon the discharge.

9. A gaseous electric discharge lamp comprising a sealed containercontaining spaced electrodes at least one of which is activated, and asealed ampule. adjacent the activated" electrode and rupturable uponoverheating at said electrode due to deactivation thereof and containingammonium sulphate salt which decomposes to yield a gaseous materialhaving a quenching effect upon the discharge.

10. A gaseous electric discharge lam comprising a sealed containercontaining spaced electrodes at least one of which is an activatedthermionic'electrode, and a sealed ampule containing a compound which isstable at the normal operating temperature of the lamp but whichdecomposes at higher temperatures to yield a gaseous material having aquenching eifect on the discharge in the lamp, said ampule being locatedadjacent the activated electrode and being rupturable upon overheatingat said electrode due to deactivation thereof.

11. A gaseous electric discharge lamp comprising a sealed containercontaining spaced electrodes at least one of which is an activatedthermionic electrode carried by a lead-in wire, and

a sealed ampule containing a, compound which. .is stable at the normaloperating temperature of the lam but which decomposes at highertemperatures to yielda gaseous material having a quenching effect on thedischarge in the lamp,

said ampule being mounted on said lead-in Wire adjacent the activatedelectrode and being rupturable upon-overheating at said electrode due todeactivation thereof. r

12. A gaseous electric discharge lamp comprising a sealed tubular glasscontainer having sheet metal terminal members sealed to itsends and.

constituting the end walls therefor, an activated thermionic electrodeat each end of the container carried by a lead-in conductor mounted onthe adjacent terminal member, and a sealed ampule containing a compoundwhich is decomposable at temperatures above the normal operatingtemperature of the lamp to yield a gaseous material having a quenchingeffect on the discharge in the lamp, said ampule being located adjacentthe activated electrode and rupturable upon overheating at saidelectrode due to deactivation thereof.

HOWARD HAYNES. LYNN S. ICKIS, JR.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Switzerland Sept. 16, 1935

